In conventional storefront and curtainwall framing systems, precise alignment of the glass lites is not critical. Because the edges of the light are received within glazing pockets formed in adjacent frame members, the edges of the lite are concealed, and minor misalignment is hidden from view.
However, with the advent of the so-called "butt-glazed" or "full view" storefront and curtainwall framing systems, in which the vertical edge of one glass lite is butted against the corresponding vertical edge of the adjacent glass lite, alignment of the glass panels became critical. Since the vertical edges of the glass lites were no longer concealed within the glazing pockets of vertical frame members, any deviation of the edge of the glass lite from vertical was readily apparent. Further, because of the considerable height of the glass lites in a storefront or curtainwall framing system, even an extremely minor misalignment of a glass lite could result in a considerable gap at the top or bottom of the joint.
Conventional practice calls for such glass lites to be leveled by inserting shims under the low end of the lite. This practice can cause problems, however, because such shims can sometimes cause the weight of the glass lite to rest on a single point, rather than being distributed across a wider area. The Flat Glass Manufacturers Association recommends that the weight of a glass lite be supported along a length of at least four inches. However, even when a four-inch long shim is used, the weight of the glass lite will often rest entirely on the "high end" of the shim, causing point contact between the glass lite and the shim which can exert undue stresses in the glass lite.
Thus there is a need for an improved arrangement for supporting and leveling glass lites in storefront and curtainwall framing systems.
There is a further need to provide an apparatus for supporting and leveling glass lites which ensures that the weight of the lite is supported along at least four inches of the lower edge of the lite.
There is still a further need for an apparatus for supporting and leveling glass lites which provides precise control over the alignment of the glass lite.